Sugar cane is one of the worlds most efficient converters of solar energy to plant material or bio-mass. Sugar cane is rated at nearly 3% efficiency of solar capture. This compares with lucerne which has an efficiency of about 0.8% and maize which has an efficiency of less than 0.5%.
In many of the tropical countries of the world there is a shortage of dietary protein. This lack of dietary protein can be traced to the lack of suitable feedstuffs for both monogastric and ruminant animals. In temperate parts of the world such animals are fed, in large part, grains which grow well in temperate climates. Sugar cane is extensively grown in tropical areas of the world and it would seem logical to utilize this material as a feedstuff for animals to increase available dietary protein in these areas. There have been a number of studies made seeking to utilize whole sugar cane or parts thereof as a feedstuff for animals. This imperative to utilize sugar cane for a purpose other than the production of refined sugar is increased as many tropical countries are in the odious position of sugar cane being their primary export, and therefore foreign exchange earner, in a world market which is saturated with the product. The market for sugar has also been reduced by the greater use of sugars derived from corn.
Unfortunately it has been found that the high fibre content of sugar cane constrains the level of production that can be achieved in ruminant animals, particularly milk yield. This is due to the fact that in fermentative digestion, as occurs in ruminants, the presence of a high sugar content in the diet restricts fibre digestion and so the high fibre levels limits the productivity that can be achieved. The high fibre content of sugar cane makes it even less acceptable for monogastric animals which cannot digest cellulosic materials.
Considerable research has been conducted in ways of overcoming the deficiencies of sugar cane as an animal feedstuff. Basically these prior art processes fall into three categories, viz:
(a) supplementing whole cane with additives, PA0 (b) utilizing a liquid fraction obtained from sugar cane such as cane juice or first molasses, and PA0 (c) using the whole sugar cane pith merely separated from the rind of the cane. PA0 (a) the rind which is made up of epidermal cells and several layers of thick walled lignified cells known as sclerenchyma cells, PA0 (b) ground tissue or parenchyma which comprises thin walled storage cells occupying a considerable part of the volume of the stalk, and PA0 (c) fibrovascular bundles scattered through the parenchyma and made up of various tissues including sclerenchyma cells, xylem, phloem and annular and spiral elements.
The first of these strategies is exemplified by an article by William S. Russell, "Sugarcane Pelletizing Plant", The Sugar Journal, January 1974, page 22. This article describes a plant which comminutes and dries whole sugar cane including, if desired, tops, leaf and dried trash. Once the cane is dried and in a semi-meal form additives such as molasses, and other materials designed to increase the protein content or to correct mineral deficiencies, are blended into the dried cane.
It should also be noted that high fibre diets generate more heat when metabolized in the animal which exacerbates the problem of animal raising under high environmental temperatures.
The second strategy is exemplified by "Intensive Beef Production" T. R. Preston and M. B. Willis, Pergamon Press, London 1970 and "Sugar Cane Juice as an Energy Source for Fattening Pigs" A. Mena, R. Elliott and T. R. Preston, Tropical Animal Production 1981, 6:338-344. These references respectively report the feeding of liquid fractions of sugar cane to ruminant and non-ruminant animals. The problems associated with this approach are outlined in "Guidelines for Pig and Poultry Production in the Tropics using Locally Available Resources" R. T. Preston, in press, wherein it is pointed out that due to the high water content of liquid fractions of sugar cane transporting the foodstuff over more than nominal distances is uneconomic, that the shelf life of the feed is short and that it is often not convenient to incorporate high-moisture feeds in large scale livestock installations which usually are designed to use dry feeds. It should also be noted that poultry are not well adapted to liquid diets in any case. It goes without saying that in almost no circumstances is it economical to dehydrate such feeds. In the case of molasses it is believed that the high concentration of soluble mineral matter of molasses (10-12% in final molasses) causes the "physiological" diarrhoea which occurs when the level of final molasses exceeds 30 to 50% in pigs. The laxative effects when final molasses is fed at high levels also depresses feed intake in pigs and poultry and causes "stress" in poultry due to the molasses sticking to the plumage. The use of high test, or integral, molasses, which is prepared from the extracted juice of sugar cane which has been clarified and partially hydrolysed to glucose and galactose to avoid the crystallization of sugar, is that the juice must be concentrated to 75.degree. Brix to stop fermentation. This concentration step is very energy consumptive and renders the process uneconomic.
The third of the major known strategies is exemplified by an article by W. J. Pidgin entitled "Derinded Sugarcane as an Animal Feed--A Major Breakthrough", World Animal Review 1974, Vol. II, page 1. This article describes a machine called a cane separator which splits the cane longitudinally and separates the soft sugar pith from the rind. The derinded material is called "Comfith" and comprises the sugar storage cells and the fibrovascular bundles but no rind. In feeding trials it was found that the fibre content from the fibrovascular bundles did limit feed intake in some monogastric animals.
The present invention is directed to a novel process for the solid phase fractionation of sugar cane which, at least in preferred embodiments, overcomes a substantial number of the problems encountered with all three of the foregoing approaches to the utilization of sugar cane as a stockfeed.